Is there a way to run a positive ground fuzz in a daisy chain power setup?

[skiraly017]

I'm really just digging into the whole fuzz thing, specifically positive ground fuzz pedals. My question is this...is there a way to run a PNP positive ground fuzz in a daisy chain power supply setup or multi-pedal/single power supply (ex. Voodoo Labs Pedal Power 2) safely without any issues? Or maybe more a better question is what's the best way to do it? I know you can convert the pedal to negative ground and run a dedicated power supply but from what I've read you run into problems using something like the PP2 or DC Brick. I found R.G. Keens article regarding +9V and -9V from one battery interesting but wouldn't you run into the same issue or would the transistor switching from the same article solve any issues? Then from Analogman's site -

"We do not like to add a power jack to these pedals, as they are a compromise with a fuzz. The germanium versions (NKT) are reverse polarity, so sharing a power source with another pedal will blow out the power source. It blows because the negative ground on normal pedals flows through the patch cord shield to the positive ground of the fuzzface, shorting out the power supply. Positive 9V in the Fuzz Face is connected to ground through your patch cords. Here is an article about the problems of using power jacks on reverse polarity pedals from Andreas in Sweden. Using a single power cable from the Voodoo Labs Pedal Power 2 would be safe though."

If I read this correctly, just wire the fuzz normally (reverse polarity) and use the appropriate cable from Voodoo Labs? I am just full of questions today, thanks in advance.

[brett]

Hi
My mind is a bit fuzzy today, but I'm fairly sure that either of these will work:
(i) you can isolate the PNP pos-ground part of a circuit (check out Tonepad's Pelusa face, which is an external neg ground, internal pos ground version of the fuzz face).
(ii) any charge pump can give you new supply voltages that are isolated from the parent supply.
cheers

[R.G.]

...is there a way to run a PNP positive ground fuzz in a daisy chain power supply setup or multi-pedal/single power supply (ex. Voodoo Labs Pedal Power 2) safely without any issues?

There are two ways.
1) use a power supply with two or more isolated outputs. I'm not familiar with the PP2 very much, but I think it has isolated outputs. If so, plug any one of them into the positive ground pedal(s).  Use other outputs for the negative ground ones.
2) make -9V from +9V, so you can use the same ground. This is what the charge pump converters I show do. In fact, I personally think that anyone building a positive ground pedal without including a charge pump converter to make -9V from an ordinary, non-isolated +9V is laying a trap for themselves and doing things the hard way. Just put the 8 pin dip and the four capacitors inside the positive ground pedal, and it now looks like a negative ground pedal from the outside. It's way cheaper than the $100+ PP2.

"We do not like to add a power jack to these pedals, as they are a compromise with a fuzz. The germanium versions (NKT) are reverse polarity, so sharing a power source with another pedal will blow out the power source. It blows because the negative ground on normal pedals flows through the patch cord shield to the positive ground of the fuzzface, shorting out the power supply. Positive 9V in the Fuzz Face is connected to ground through your patch cords. Here is an article about the problems of using power jacks on reverse polarity pedals from Andreas in Sweden. Using a single power cable from the Voodoo Labs Pedal Power 2 would be safe though."

IMHO, this is shortsighted. "Just say no." went out with Nancy Reagan.

[frank_p]

RG is quicker with his photon gun but I was typing at the same time and you'll have an example of someone who was also confused.

http://www.diystompboxes.com/smfforum/index.php?topic=78077.msg642363#msg642363

If you want do daisy-chain you have to make a charge pump circuit or change your pedal's guts like Brett said (but can be tricky).  The other solution is having an other isolated power supply.  If the output of your power transformer is not completely separated from the rest, you create a short via the output secondary and the sleeve side of your patch cord.  Some report a charge pump is a bit noisy.

What happens if you do otherwise is that there is no common ground anymore because it becomes the power of the other.  The evil twins will be battling for power and one of them will die.  A power source can not be +9V and -9V at the same time unless its a floating 18V with a ground in the middle.

Nancy, don't know her...  I'll stay with the beavers...  My 5 cents.

[skiraly017]

Thanks to everyone who chimed in. I'll make it happen if it kills me. 

[SlashLP97]

I don't know a whole lot about fuzz pedals specifically, but I know alot about generic BJT, MOSFET and JFET amplifiers.  Is there any reason you couldn't hook up the +9V supply to the collector of the PNP device you are using, have the output at the emitter, then through the bias resistor to ground.  You still have a 9V drop from collector to ground, and the transistor doesn't care if that 9V is from 0 to -9V or +9V to 0V.

Is there a problem with that logic?

[earthtonesaudio]

I don't know a whole lot about fuzz pedals specifically, but I know alot about generic BJT, MOSFET and JFET amplifiers.  Is there any reason you couldn't hook up the +9V supply to the collector of the PNP device you are using, have the output at the emitter, then through the bias resistor to ground.  You still have a 9V drop from collector to ground, and the transistor doesn't care if that 9V is from 0 to -9V or +9V to 0V.

Is there a problem with that logic?

I think you must mean "hook up +9V to the emitter..." or put another way, just ground the other end of the battery.  Yes this works, most of the time.  In fact a huge percentage of integrated circuits have NPN and PNP devices co-existing in harmony and will work from a variety of power supply configurations.

However, the "most of the time" part is that sometimes, for reasons not fully understood to members of this forum, certain vintage fuzz circuits will oscillate if you don't keep their Ground as 0V.

[jacobyjd]

In my experience, a Pedal Power 2 is the best thing a DIY-er can have on their board. All the outputs are isolated, AND you can run daisy chains off those.

I've used one output for a chain of 3 positive ground pedals before, while using all the other outputs for negative gnd pedals.

Plus you get 9, 12, 18 and 24v depending on how you set it up. Want to run your mutant, freak-ass fuzz pedal on -18v? Done.

[SlashLP97]

Thanks for clearing that up, I had been wondering about it for a while.  Maybe a ground loop problem?  They don't teach us any of this practical stuff in school, just lots of ideal garbage.